Rejection rates of body-powered hands are higher than that of hooks. Body powered hands are inefficient. As a result they require an uncomfortable high activation force, and produce a relatively low pinch force in return (<15 N). Also they have stiff fingers, which do not adapt to the shape of the grasped object. Despite all the drawbacks of the current hands, the design of body powered hand prostheses almost has not changed since the 1950’s. The activation force has not been reduced. The pinch force is still low, and hand prostheses are still quite heavy. There have been attempts to increase the efficiency of body powered hand prostheses, by using hydraulics. However, these studies have not resulted in the commercial application of hydraulics in body powered arm prostheses.